Pulmonary stenosis is characterized by obstruction to outflow from the right ventricle due to a defect in the pulmonary artery, pulmonary valve, or right ventricle itself. It one of the more common congenital heart defects and is often associated with major, primary, cardiac anomalies.

The most common type of obstruction is stenosis of the pulmonary valve as a result of either complete absence or fusion of leaflets. In most cases, the valve forms a dome-like structure with a variably sized orifice through which a jet of blood can flow through. This pattern of flow results in dilation of the left main pulmonary arteries that receive the jet of blood and depending on the degree of stenosis, hypertrophy of the right ventricle.

Obstruction within the right ventricle is less common and often occurs as a result of a ventricular septal defect that displaces the moderator band. Stenosis of the peripheral pulmonary arteries can be due to any number or combination of lesions including those that originate in the main pulmonary artery and those found at more locations either unilaterally or bilaterally.

Stenosis of the pulmonary outflow tract necessitates an increase in ventricular pressure in order to overcome the obstruction and provide sufficient cardiac output. Over time, the increased pressure leads to hypertrophy and decreased compliance of the right ventricle which in turn requires pressure in the right atrium to increase in order to fill the right ventricle. If the foramen ovale persists and pressure in the right atrium becomes greater than left blood may begin to shunt right-to-left.

Infants born with significant pulmonary stenosis appear cyanotic at birth due to right-to-left shunting and are dependent on a patent ductus arteriosus for adequate blood supply. Because this is a life-threatening condition, it is recommended that balloon dilation be performed to relieve the obstruction as soon as possible.

Uncomplicated stenosis of the pulmonary valve is one of the most common congenital heart defects and also the easiest to manage. Infants born with this defect are typically diagnosed at birth on routine physical exam and murmur heard on auscultation. In the absence of septal defects, these children are often asymptomatic.

Balloon dilation of the valve is the treatment of choice in cases where a significant pressure gradient exists across the stenotic valve. When pressure gradients are low, most patients do not need any form of treatment and require no restrictions on activity.

Peripheral pulmonary stenosis is a common diagnosis diagnosed by auscultation revealing an ejection murmur heard in all parts of the chest. These obstructions often regress over time and require little-to-no intervention.